The present invention generally relates to a seat detector e.g. for use in an automotive vehicle.
In modern vehicles, seat occupancy sensors are widely used in order to detect whether a passenger seat is occupied or not. The information about the occupancy of the passenger seat may then be used in order to control the deployment of one or more airbags associated to the vehicle seat (the deployment is e.g. inhibited if the vehicle seat is found to be non occupied).
Today's automotive safety standards require automotive vehicles to be equipped with seat belt reminder systems for reminding a vehicle passenger to fasten the seat belt associated to the occupied vehicle seat. Such seat belt reminder system comprise typically a seat occupancy sensor for detecting an occupancy of a vehicle seat and a seat belt sensor, e.g. a buckle switch sensor, for detecting whether a seat belt is fastened or not.
While until now, those seat sensors where mainly associated with the front seats of the vehicle e.g. for controlling airbag systems associated to the front seats or for generating warning signals relating to the fastening of the seat belts associated with the front seats, future standards will require that also rear seat be equipped with such seat occupancy sensors and seat belt reminder systems.
The seat occupancy sensors used in airbag control systems or seat belt reminder systems usually comprise pressure sensing devices integrated in the respective passenger seat for detecting a pressure induced by the presence of a passenger into the seat. The pressure sensing devices, as e.g. disclosed in DE-A-42 37 072, comprise a plurality of individual force sensors, which are connected in a suitable manner to a control unit designed for measuring a pressure depending electrical property of said individual pressure sensors. These occupancy sensors have proven to be very reliable and well adapted to the detection of seat occupancy.
The seat belt fastening detectors of seat belt reminder systems typically comprise mechanical or magnetic buckle switches for detecting, whether a latch of the seat belt is inserted into the seat belt buckle. One such buckle switch is e.g. disclosed in U.S. Pat. No. 5,871,063. As an alternative to the buckle switches, seat belt fastening detectors have been proposed which generate a buckled/unbuckled signal based on the tension in the seat belt.
One drawback of these known seat sensors lies in the fact, that the seat occupancy sensor and/or the seat belt fastening detector have to be physically connected to the control unit by means of connection wires in order to be functional. This need for physically connecting the sensing device to the control unit however causes problems especially in modern cars equipped with a flexible seating system with removable and/or displaceable back seats.